1. Field of the Invention
The present invention relates to a device for correcting the speed of an automotive vehicle engine provided with a variable speed transmission equipped with a mechanism for controlling its operation.
2. Summary of the Prior Art
In automotive vehicle transmissions with change-speed mechanisms, it is known to provide for control of the operation of the change-speed mechanism by means of a control mechanism. This mechanism generally comprises a hydraulic senser having a movable part capable of actuating the control member for speed reduction of the change-speed mechanism. The hydraulic senser is arranged either to be supplied with pressure fluid, or to communicate with exhaust by means of a distributor valve, of which the slide is subjected to opposing forces, generated by a centrifugal governor, and a resilient member.
The centrifugal governor exerts an action which is a function of the speed of rotation of the engine. The resilient member is connected to an acceleration control member of the vehicle or to the accelerator pedal. When the action of the centrifugal governor is overriding, the slide of the distributor valve is so disposed that the hydraulic senser effects a reduction in the speed-reducing ratio. In contrast, when the action of the resilient member is overriding, the distributor valve slide is displaced into a position such that the hydraulic senser effects an increase in the reduction ratio.
In the case when the change-speed mechanism is in its position for greatest speed reduction ratio and substantial acceleration is required, the vehicle being stationary, the engine speed rapidly increases to normal speed and uses a part of its power to accelerate itself. At the instant when the engine reaches the controlled normal operating speed, it can then generate its full power and it gives rise to hesitation in operation if the engine operating speed is high. If it is low this hesitation in operation will not happen. Moreover, the time response of the centrifugal governor is such that when the engine increases in speed to its operating speed very rapidly, it may exceed its control speed before the governor has reacted thus giving rise to another cause of hesitation in operation or momentary stall at the instant when it acts. It is therefore necessary to limit the control operating speed of the engine in the case where the change-speed mechanism is in its position of greatest speed reduction and when high acceleration is required.
Systems limiting the normal operating speed of an engine are known, when the speed of the vehicle is low such that the speed governor is in a position of high reduction and the accelerator pedal is kicked down. These control systems include centrifugal governors rotated by the output shaft of the change speed mechanism and of which the action tends to oppose the action of the centrifugal governor.
An object of the present invention is to resolve the problem posed by means of a correcting device having a simple kinematic form enabling the omission of accessories, often of complex form, in the transmission system.